1) Field of the Invention
This invention relates to a new modulator topology that combines solid-state switches in a high voltage, high current array which avoids the difficulties inherent to other array geometries.
2) Description of the Prior Art
This invention was made with the United States Government support under grant number DE-FG03-96ER82172 awarded by the Department of Energy. The Government has certain rights in this invention.
Schemes for producing high voltage pulses are known. For example, U.S. Pat. No. 5,038,051 to Firman et al., describes a Solid State Modulator For Microwave Transmitters. The switching modulator of Firman et al. uses a plurality of individual primary windings coupled to a single secondary winding. The voltage generated in the secondary winding is proportional to the sum of the excitation of the primary windings. Each of the primary windings is individually switchable for regulating the generated output voltage at the secondary winding. However, this prior art modulator is uniquely unipolar (due to the presence of the diodes employed). Bipolar construction is needed to reset the transformer core. Additionally, Firman et al. has no local energy storage capability in each of the modules.
In accordance with U.S. Pat. No. 5,326,970 to Bayless, a Method and Apparatus for Logging Media of a Borehole is disclosed. Like Firman et al., there is no provision for any local energy storage in each module. Further, a single pulse generator is used to energize all of the induction modules. Due to the method used to reset the induction cores, the duty cycle of this device is intrinsically limited. Additionally, the core reset current does not recharge the capacitors. Finally, the primary pulses are high voltage, greatly exceeding the voltage which could be switched with a single solid-state device.
U.S. Pat. No. 5,601,633 to Ponizovsky discloses a High Voltage Electrical Method for removing ecologically noxious substances from gases using a multi-Stage Fitch pulse modulator which produces a high level pulsating voltage superimposed on a constant direct current voltage. The Fitch pulse generator produces a high voltage output pulse by adding the individual stage voltages electrostatically, rather than electromagnetically as in the present invention. Further, the Fitch pulse modulator requires high voltage switches; air spark discharges, vacuum discharges, or gas filled discharge tubes. These are not solid-state devices. Therefore, the Fitch pulse modulator would require more frequent service and incur higher operating costs than the present invention.